From: Phil Tomson <rubyfan@...>
Date: 2006-06-04T06:35:24+09:00
Subject: Re: Where can one find examples of masterful Ruby code?

On 6/3/06, Alder Green <alder.green@gmail.com> wrote:
 >
> For example: check if integer i is a power of 2, with an expression no
> more than 13 characters long.
>
> Solution: (i & (i - 1))
>
> Note that this solution is not only very concise, but also (on any
> reasonable implementation) very fast. Masterful code has a tendency to
> be "correct" in many ways.
>

Thanks for this very useful snippet.  It was worth reading the thread for.

Probably should be methodized as:
  def powerof2?( i )
    (i & (i - 1))==0
  end

Of course it's not immediately obvious from reading the code how it
works till you try an example:

   1000  #8 in binary
   0111  #7 in binary
 &----------
   0000

...so maybe readability isn't always part of the criteria for
'masterful' code.  I do think that the way you've done it is the
fastest way to figure out if an integer is a power of 2 and after you
work through an example it does seem quite elegant.

Phil